Similar to the spectroheliograph, but used for visual instead of photographic purposes.

A line drawn through all points on a map having the same amount of cloudiness.

An automatic, recording cloud height indicator.

An instrument for measuring radiant energy. It consists of an ether differential thermometer with blackened bulbs. One of the bulbs is exposed to the unknown radiation and the other to a black body source whose temperature can be varied. Equality of radia ...

Same as evaporative power.

Same as mirror nephoscope.

A pressure-plate anemometer consisting of a plate which is free to swing about a horizontal axis in its own plane above its center of gravity. The angular deflection of the plate is a function of the wind speed. This instrument is not used for station mea ...

The level at which ice crystals and snowflakes melt as they descend through the atmosphere.

An instrument for measuring the difference of the solar radiation falling on both sides of a horizontal surface from the whole hemisphere.

A photometric unit of illuminance or illumination equal to one lumen per square meter

A halo phenomenon consisting of a horizontal circle passing through the moon, corresponding to the parhelic circle through the sun. Produced by reflection of moonlight from ice crystals.

Literally "not wet", containing no liquid.

An area of low atmospheric pressure which has a closed circulation that is cyclonic (counterclockwise in northern hemisphere and clockwise in southern hemisphere).

The process by which events in the real world are translated into machine-readable signals.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

Contraction for radiosonde observation.

A type of photoelectric photometer used to measure high-altitude winds on the assumption that stellar scintillation is caused by atmospheric inhomogeneities being carried along by wind near the tropopause level.

The attenuation of light.

A device used on certain types of instruments to prevent unwanted radiation from affecting the measurement of a quantity. Also called solar radiation shield.

A wave resulting from the action of wind on a water surface.